As the boy kicks the football with an angle, due to the effect of the gravitational force, the ball would follow a projectile path which is parabolic in nature. From this idea, we can derive equations pertaining to the maximum height that the ball would reach. At the maximum height of the ball, the velocity of the ball would be equal to zero. From the equations for projectile motion, we would obtain the equation as follows:
Maximum height = v0^2 sin^2 (theta) / 2g
Maximum height = (28.0 m / s )^2 sin^2 (30.0) / 2(9.8 m / s^2)
Maximum height = 10 m
The maximum height that the ball would reach would be 10 m.